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The Nose Knows: Smell Disorders

Amy Campbell

February 19, 2013

Some of my favorite smells are a Christmas tree, chocolate chip cookies baking in the oven, and freshly cut pumpkins at Halloween — I can’t imagine not being able to smell these delightful things. But according to the National Institutes of Health, between 1% and 2% of people in North America say they have a smell disorder. About 25% of men age 60–69 and 11% of women in this same age range have difficulty being able to smell.

Not being able to smell, either somewhat or at all, can be dangerous, as our noses alert us to smells that can signal danger, such as a fire, a gas leak, or spoiled food. It can also be a sign of a serious medical problem.

How our sense of smell works
We have special cells in our noses called olfactory sensory neurons. These cells are connected to the brain, and when they’re stimulated by something, like popcorn popping at the movie theater, the neurons send a message to the brain, which identifies the smell.

Smells reach these sensory neurons through our nostrils and also through our the roof of our throats. When we eat, scents are released that reach the sensory neurons. This is why taste is so closely connected to our sense of smell. Think of when you have a cold or allergies and your nose is all stuffed up: you can’t smell much of anything, and the food that you eat seems to have no flavor. Or it tastes like paste.

We also have nerve endings in our eyes, nose, mouth, and throat that can detect more irritating smells, like onion, ammonia, or peppermint.

Causes of smell disorders
If you have a smell disorder, you may have a reduced ability to smell, called hyposmia, or a complete inability to smell, called anosmia. A condition known as dysosmia is when pleasant odors now smell unpleasant (or vice versa), or when odors otherwise smell unusual. You may find that something that usually smells a certain way now smells different. Or, it could be that what once smelled nice now smells bad.

There are many possible causes of smell disorders, including the following:

• Nasal polyps
• Sinus or upper respiratory infections
• Injury to the nose from surgery or head trauma
• Dental problems
• Hormone imbalances
• Nutrient deficiency
• Exposure to toxic chemicals
• Radiation to the head or neck
• Chemotherapy
• Medicines, including antibiotics, antidepressants, and heart medicine
• Drug and alcohol abuse
• Smoking
• Aging
• Medical conditions, including Parkinson disease, Alzheimer, multiple sclerosis, and diabetes

According to one neurologist, about half of people with diabetes have a diminished sense of both smell and taste.

Diagnosing a smell disorder
Smell disorders often go undiagnosed because the loss of or alteration in ability to smell can happen gradually. In many cases, people go to their doctor as a result of not being able to taste their food. However, the issue has to do with a change in their ability to detect smells. Your doctor may refer you to an ear, nose, and throat doctor (called an otolaryngologist). He will do a physical exam of your ears, nose, and throat and may have you undergo certain tests, including smelling tiny beads filled with specific odors. You might also need a CT scan, as well.

Treating smell disorders
If you have a smell disorder, don’t assume that it can’t be treated. The first step is to find out what the cause is. Treatment of a smell disorder depends on the cause. For example, congested sinuses from a cold or from allergies will usually clear up on their own or with decongestants. Any congestion that doesn’t go away after several days may signify an infection, which could require antibiotics. Nasal polyps or growths will likely require surgery. If a particular medicine is suspected of altering your sense of smell, talk to your doctor about other treatment options. Hormonal or nutritional deficiencies can usually be corrected, as well. And if you smoke, drink too much alcohol, or use drugs, the obvious solution is to stop.

Unfortunately, smell disorders can’t always be treated. The damage to nerve cells from head injury or radiation can’t be treated. A loss of smell from various medical conditions may not be able to be treated, either.

In the meantime, you may be able to protect and even enhance your sense of smell, according to an article published in last week’s Wall Street Journal. In the article, Dr. Alan Hirsch, the director of the Smell & Taste Treatment and Research Foundation in Chicago, describes using “sniff therapy.” He says to choose three or four different pleasant scents, like a floral scent from a shampoo, a fruity scent from a piece of fruit, and one or two other scents, like vanilla extract or coffee. Don’t choose anything irritating, like an onion. Sniff these scents four to six times a day to get those nasal scent receptors working. Also, take the time to eat slowly and chew your food well. Doing so can release more flavor from food.

Talk to your health-care provider if you think you’ve lost some or all of your ability to smell. It’s important to rule out any serious causes and also to explore treatment options.

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